The present invention relates to measurement of the flow of solids pneumatically conveyed through a hose and particularly, to electronic flow meters for measuring the flow of insulation passing through the hose of an insulation blowing machine.
For installing blown insulation, the industry has established recommended guidelines for insulation density per square foot of area covered. The present method of measuring the amount of insulation blown is to count the number of standard-sized bags consumed in the blowing operation, and the consumer relies on the contractor to use the proper number of bags. With this method of measurement, however, the industry has suffered a fraud problem. This problem is documented in the INSULATION PROFESSIONAL, Spring, 1983, a publication by Owens-Corning Fiberglas Corporation, and in the ICAA NEWS, June 1983, a publication by the Insulation Contractors Association of America. The problem is characterized by some contractors puffing the insulation with air and thinly spreading it so that fewer bags of insulation per square foot are installed than the industry guidelines require. After the insulation has been installed, it is impossible to measure the amount that was actually blown without removing and weighing it.
Various flow measuring devices are known for sensing characteristics of materials passing through a conduit. For example, U.S. Pat. No. 4,231,262, issued to Richard H. Boll et al on Nov. 4, 1980, teaches the use of a flow meter for measuring the flow of particulate solids by taking differential pressure measurements along points of a venturi through which the solids are funneled; and U.S. Pat. No. 3,800,147, issued to James J. Shea et al on Mar. 26, 1974, discloses the use of a turbidimeter with automatic color compensation for sensing low turbidity concentrations in fluids of various colors. However, neither of these devices is capable of measuring the flow of bulk solids, such as loose fill insulation.